Abstract
ABSTRACT Previous ecological studies of dioecious plant species have found that female plants preferentially occur at lower altitudes where there are typically better nutritional conditions, while male plants often occur in less favorable sites. We compared the ecophysiological performance of male and female plants in three populations of the dioecious Baccharis concinna, an endemic species of rupestrian grasslands of Serra do Cipo, in southeastern Brazil. We hypothesized that physiological differences between the sexes would explain the distribution patterns of the populations. Analyses of the tissue content of phosphorus (P), calcium (Ca), potassium (K) and sodium (Na), and carbon and nitrogen stable isotopes, were used to assess nutritional status and water use efficiency (WUE) in plant leaves, stems and roots of male and female plants in three populations located along an elevational gradient. Differences among populations were related to decreased nutrient levels and WUE at higher elevations, but an effect of sex was found only for %C, with male plants having slightly higher values. In conclusion, the sex ratios in the studied populations of B. concinna could not be attributed to differences in nutrient acquisition and WUE.
Highlights
Many aspects of the natural history, ecology, and physiology of dioecious plants have been studied in an attempt to unravel the evolutionary processes and mechanisms involved in the differential distribution of the sexes among habitats of differing quality (Lloyd 1973; 1974; Freeman et al 1976; Varga & Kytöviita 2011; Castilla et al 2012)
The effect of plant sex was restricted to the leaves of B. concinna, and only for %C (Tab. 1), with the average value for males of all three populations being higher than the average for female plants
Male and female plants of dioecious species may differ in traits related to plant phenology and defense against herbivory, as well as in physiological traits such as photosynthetic performance and water use (Dawson & Geber 1999; Rowland & Johnson 2001; Cornelissen & Stiling 2005; Vega-Fruits et al 2013)
Summary
Many aspects of the natural history, ecology, and physiology of dioecious plants have been studied in an attempt to unravel the evolutionary processes and mechanisms involved in the differential distribution of the sexes among habitats of differing quality (Lloyd 1973; 1974; Freeman et al 1976; Varga & Kytöviita 2011; Castilla et al 2012). The spatial segregation of males and females of dioecious plants among habitats has been mostly attributed to sex-dependent differential resource requirements (e.g., Cox 1981; Meagher 1984), in which female plants allocate more resources to reproduction, and preferentially occupy relatively more favorable habitats (e.g., Bierzychudek & Eckhart 1988; Krischik & Denno 1990; Herms & Mattson 1992).
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